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Apr 11, 2024 · The NAVD88 tidal datum refers to the use of the North American Vertical Datum of 1988 (NAVD88) to measure heights above the geoid, which is an idealized surface approximating mean sea level. It accounts for tides and other factors to determine accurate elevations above the reference surface.
Oct 29, 2023 · These datums are used to measure the height (altitude) and depth (depression) above and below mean sea level. Commonly used vertical datums in North America are the National Geodetic Vertical Datum of 1929 (NGVD29) and the North American Vertical Datum of 1988 (NAVD88). A (vertical) geodetic datum often ties in tidal datums.
NAVD 88, was completed in June 1991. It is now the only official vertical datum in the United States. NAVD 88 was created by adding 625,000 kilometers of leveling, performed after NGVD 29 was established, and by performing a major least squares adjustment that constrained only a single tide station at zero elevation.
A: Elevations referenced to NAVD88 (North American Vertical Datum of 1988) should never be used as Mean Sea Level. This is one of the most common mistakes made by someone who is new to working with elevations in the coastal zone and you are not alone - confusion about how local MSL relates to published geodetic elevations has existed as long as we have had national geodetic datums.
MEAN TIDE LEVEL (MTL) = 0.868 MEAN SEA LEVEL (MSL) = 0.861 MEAN LOW WATER (MLW) = 0.287 NORTH AMERICAN VERTICAL DATUM-1988 (NAVD) = 0.062 MEAN LOWER LOW WATER (MLLW) = 0.000 LOWEST OBSERVED WATER LEVEL (12/17/1933) = -0.832 Bench Mark Elevation Information In METERS above: Stamping or Designation MLLW MHW
Sep 12, 2023 · NAVD 88 is measured using the Helmert orthometric height, which calculates the location of the geoid (approximating mean sea level) from modeled local gravity. The NAVD 88 model is based on measurements taken at the time of its establishment and remains fixed despite later improved geoid models.
NAVD 88 and IGLD 85 are identical. However, NAVD 88 bench mark values are given in Helmert orthometric height units while IGLD 85 values are in dynamic heights. See International Great Lakes Datum of 1985, National Geodetic Vertical Datum of 1929, and geopotential difference. NAVD 88 should not be used as Mean Sea Level.
